Device comprising gas cushion, in particular for a motor vehicle

ABSTRACT

The invention relates to a device comprising a gas cushion ( 3 ) that can be inflated with gas by means of a filling device, in addition to a transceiver ( 5 ) for electromagnetic waves ( 6 ) and an evaluation device ( 8 ) that is connected to the latter. At least one interrogation unit ( 4 ), which can be interrogated in a contactless manner by the transceiver ( 5 ), is located on the gas cushion ( 3 ). This permits the provision of information in the evaluation device ( 8 ) concerning the degree of deployment and/or the deployment speed of the gas cushion ( 3 ).

[0001] The deployment behavior of a gas cushion in a motor vehicle is usually designed to cover a situation in which the vehicle driver or a passenger is held by the safety belt with their back against the backrest of the seat, in other words is at a certain distance from the gas cushion deploying in a collision situation and usually falls forward into the already inflated gas cushion. It can however happen that the driver or a passenger is actually leaning forward at the time a collision situation occurs and as a result is hit by the deploying gas cushion. This so-called “Out-of-Position” (OoP) situation has already led to more serious injuries than would have resulted due to the actual collision alone without the gas cushion. Consequently, concepts have already been developed which detect the deployment behavior of the gas cushion and in the event of an obstacle being present in the deployment range of the gas cushion which leads to a reduced or even inhibited deployment prevent further inflation of the gas cushion.

[0002] A device in which the gas cushion is provided with interrogation units which are implemented as threads or tapes and comprise a scannable coding is known from EP 0 812 741 A1. When the gas cushion is deployed, the threads or tapes are drawn along at the velocity of the front part of the gas cushion and stretch to a corresponding length in the interior of the gas cushion. An evaluation device scans the coding either mechanically or also capacitatively, inductively, optically or the like and in this way can determine whether there is an obstacle in the deployment range of the gas cushion. If such an obstacle is detected, the gas supply is reduced or stopped altogether in order to avoid an injury to a person forming the obstacle.

[0003] However, problems with the known device are a complicated and therefore expensive manufacturing process and unsatisfactory reproducibility of the measurement result.

[0004] The object of the present invention is therefore to specify a device of the aforementioned type which avoids these problems.

[0005] The object is achieved by a device according to claim 1.

[0006] Advantageous developments of the invention are specified in the subclaims.

[0007] Accordingly, the device according to the invention is implemented with a transceiver for transmitting and receiving eletromagnetic waves which is preferably disposed in the dashboard of a vehicle having the device. The transceiver transmits electromagnetic waves to one or more interrogation units disposed on the gas cushion which in turn send back a wave identifying a particular interrogation unit, said wave being received by the transceiver and processed and evaluated by an evaluation device connected to the transceiver in order to be able to effect an appropriate response to the deployment behavior of the gas cushion.

[0008] In contrast to the prior art, the interrogation units can therefore be interrogated in a contactless manner, thus removing the need for complicated mechanics. The deployment velocity can be determined in a relatively simple and yet precise and very easily reproducible way from the Doppler shift of the waves coming from the interrogation units.

[0009] In a first embodiment one interrogation unit is implemented as a simple reflector. If only one interrogation unit is present, this is entirely adequate to obtain a fully operational implementation of the invention.

[0010] With a plurality of interrogation units, it should be possible to distinguish these from one another, which means that the reflectors are advantageously implemented as polarizing, preferably circularly polarizing, reflectors. If opposite polarizations are chosen, two interrogation units can already be distinguished.

[0011] In order to be able to differentiate or recognize a greater number of interrogation units it is advantageous to implement these as transponders, in other words as units which receive the wave coming from the transceiver, store at least a part of the wave's energy as power for supplying a logic circuit and return an encoded wave, i.e. a wave modulated by means of a code.

[0012] In this case the logic circuit can be implemented in its simplest form as a switch which merely switches a transceiver antenna on or off according to a stored code. Also conceivable, however, is a more complicated logic circuit which permits a correspondingly more complicated coding. For example, the logic circuit can also be implemented by means of an oscillator which actively generates a signal which, upon excitation by a signal or wave, is transmitted back to the transceiver as a wave. In this case each interrogation unit can transmit at a different frequency. It is similarly possible to use different modulations at the same frequency or something similar. It is important in any event that the signals of the individual interrogation units can be distinguished by the transceiver.

[0013] The invention is explained in more detail below by means of an exemplary embodiment and with reference to a FIGURE.

[0014] The FIGURE shows a schematic cross-sectional representation of a vehicle cockpit with a seat 1 and a person 2 sitting on the seat.

[0015] An inflated gas cushion 3 is realized with a plurality of interrogation units 4 which can be implemented as simple reflectors or as transponders. Information on suitable transponders can be found at the Internet site “http://rapidttp.com/transponder/”. A transceiver 5 which is connected to an evaluation device (8) transmits electromagnetic waves 6 to the interrogation units 4. These send back suitably coded waves 7 which are received by the transceiver 5 and processed by the evaluation device (8). 

1. A device comprising a gas cushion (3) which can be inflated with gas by means of a filling device, as well as a transceiver (5) for electromagnetic waves (6) and an evaluation device (8) connected to this transceiver, wherein there is disposed on the gas cushion (3) at least one interrogation unit (4) which can be interrogated in a contactless manner by the transceiver (5) and as a result information about the degree of deployment and/or the deployment velocity of the gas cushion (3) is provided in the evaluation device (8).
 2. The device according to claim 1, characterized in that an interrogation unit (3) is implemented by means of a reflector.
 3. The device according to claim 2, characterized in that the reflector is a polarizing reflector.
 4. The device according to claim 1, characterized in that an interrogation unit (3) is implemented by means of a transponder.
 5. The device according to claim 4, characterized in that a transponder is implemented by means of a logic circuit which enables an encoded wave (7) to be transmitted back to the transceiver (5). 